Hydrocracking process using platinum/alumina catalyst activated and cooled with hcl

ABSTRACT

An improved halogen-activated platinum/alumina catalyst is produced by activating in the presence of a relatively high concentration of HCl treating agent and thereafter slowly cooling in the presence of a relatively low concentration of HCl treating agent.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation-in-part of copending application Ser. No 664,217filed Mar. 5, 1976 (now U.S. Pat. No. 4,003,956), which in turn is adivisional Ser. No. 458,700 filed Apr. 8, 1974, now U.S. Pat. No.3,970,589.

BACKGROUND OF THE INVENTION

This invention relates to a process of producing improvedplatinum/alumina catalyst by activating with a hydrogen chloridetreating agent.

It is known in the art to utilize halogen treating agents in theactivation of active alumina containing catalysts. It has been found,however, that the effectiveness of such treatments can vary widely, andin particular can be decreased when the cooling time for the activatedcatalyst is relatively long as is generally the case in a commercialoperation.

SUMMARY OF THE INVENTION

It is an object of this invention to provide a hydrocarbon conversioncatalyst of improved activity; it is a further object of this inventionto provide a process for hydrogen chloride activating a platinum/aluminacatalyst which is applicable to commercial scale operations; it is yet afurther object of this invention to provide a process for hydrogenchloride activation of a platinum/alumina catalyst wherein the coolingtime after activation is relatively long; and it is still yet a furtherobject of this invention to achieve improved isomerization conversions.

In accordance with this invention, a platinum/alumina catalyst isproduced by activating in the presence of a relatively highconcentration of hydrogen chloride and thereafter slowly cooled in thepresence of a relatively low concentration of hydrogen chloride.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Myers, U.S. Pat. No. 3,449,264, issued June 10, 1969, broadly discloseshalogen activation of active alumina catalysts, the invention hereinbeing an improvement over the basic invention of said Myers patent.

The active platinum/alumina catalysts which are prepared in accordancewith this invention are basically platinum supported on an activealumina base. These catalysts are well known in the prior art. Theycontain from 0.01 to 10, preferably 0.1 to 1, weight percent platinumbased on total catalyst weight on the alumina base. These catalysts canalso contain a minor amount of halogen incorporated during preparationof the catalyst, chlorine and/or fluorine being the two halogenscommonly present. Although one or both of these halogens can be presentin the catalyst prior to activation by the process of the presentinvention, the catalyst containing them is not the equivalent of thecatalyst which has been activated by the present process. The amount ofhalogen in the catalyst as prepared (i.e. prior to activation inaccordance with this invention), if any, is usually less than about 1.5weight percent of the catalyst.

To produce these catalysts, an alumina, well known in the art as an"active" alumina, is essential. Active aluminas may be syntheticallyprepared as by calcination of alumina gels which are formed by addingsuch reagents as ammonium hydroxide to a salt of aluminum, such asaluminum chloride or aluminum nitrate. These aluminas are generallygamma or eta aluminas depending upon the dehydrating conditions used.Similar active aluminas may be prepared by calcination of naturallyoccurring aluminas such as the monohydrate and the trihydrate. Bauxiteis a common source of active alumina when properly calcined anddehydrated. The alumina base of the catalyst may contain minor amountsof silica and boron oxide. The amounts of these materials should be lessthan about 30 weight percent, and preferably less than about 10 weightpercent of the catalyst base components to produce the most activecatalysts.

The alumina supported platinum catalysts are first activated withanhydrous HCl and thereafter cooled while in contact with anhydrous HCl.

During the activation step the platinum metal-alumina or platinummetal-halogen-alumina catalyst is heated in the presence of the treatingagent at a temperature of 600°-1500° F., for a period of at least 0.1hours and up to 100 hours or more, preferably one-half to six hours.Suitable conditions are one-half to four hours at 900°-1500° F. withoutthe HCl followed by 1/2 to 4 hours at 900°-1500° F. in contact with theHCl. The treating agent may be carried in a dry carrier gas. If acarrier gas is used, the treating agent concentration is preferably atleast about 30 volume percent and more preferably over about 60 volumepercent HCl based on the total volume of HCl gas and carrier gas; thus30-100 percent hydrogen chloride is suitable, 40-75 percent beinggenerally preferred.

Generally the cooling time will be at least 0.5 hours, preferably 0.6 to10 hours. The volume percent of hydrogen chloride gas during the coolingstep must be within the range of 1 to 20, preferably 2 to 16, morepreferably 2 to 6 volume percent based on the total volume of HCl gasand carrier gas. The carrier gas can be hydrogen, nitrogen, methane,ethane, or any other gas essentially inert in the treating process, ormixtures of such gases. A mixture of hydrogen and nitrogen is preferred,the mixture preferably containing 5 to 50 weight percent hydrogen. Thecooling time referred to is the time to cool from the activationtemperature of 900°-1500° F. to about 200° F. to 400° F. Below 400 thepresence or absence of HCl has little effect on the catalyst; below 200°F. it has no effect. Thus once the temperature reaches 200°-400° F.there is nothing critical about the way it is treated so long as it isnot subjected to obvious poisons such as water.

The carrier gas can be hydrogen, nitrogen, methane, ethane or any othergas essentially inert in the treating process or mixtures of such gases.Preferably the carrier gas in the activation step is hydrogen, and inthe cooling step the carrier gas is preferably either hydrogen or amixture of hydrogen and nitrogen.

Preferably the catalyst is activated at pressures somewhat higher thanatmospheric, i.e., 10 psig. In most instances the pressure will bewithin the range of 0-25 psig.

The catalysts of the present invention are particularly applicable tothe isomerization of isomerizable hydrocarbons including acyclicparaffins, and naphthenes. These catalysts are particularly suitable forthe isomerization of straight chain paraffins containing four to eightcarbon atoms per molecule including n-butane, n-pentane, n-heptane, andthe like. Some examples of naphthenes which can be isomerized with thesecatalysts are methylcyclopentane, dimethylcyclopentane, cyclohexane,methylcyclohexane, and the like. Actually these are equilibriumreactions as follows:

cyclohexane ⃡ methylcyclopentane

methylcyclohexane ⃡ dimethylcyclopentane

pentane ⃡ methylbutane

n-hexane ⃡ methylpentanes ⃡ dimethylbutanes

Conditions can be adjusted to give hydrocracking, as for instance toproduce butane from n-octane. Preferred process conditions forhydrocracking are as follows. Pressure: 50-5000 psig, preferably100-3000 psig; temperature: 200°-800° F., preferably 300°-700° F.;liquid hourly space velocity: 0.1-30, preferably 0.5-20; andhydrogen/hydrocarbon mole ratio: 0.5-30, preferably 2-20. Applicablefeeds include C₅ and higher boiling hydrocarbons such as naphthas anddistillates. The catalyst is especially useful in hydrocracking toproduce C₄ and lighter hydrocarbons. Feeds should be substantially freeof poisons such as water, oxygen-containing organic compounds and sulfurcompounds.

The isomerization condition and recovery procedures can be varied toachieve the desired conversion in a manner known in the art. Mostpreferred is normal butane which is isomerized to isobutane.

Hydrocarbons to be isomerized are contacted with the activated catalystsprepared in accordance with the invention at an isomerizationtemperature of about 100°-600° F., more preferably 150°-450° F., in thepresence of free hydrogen. The hydrogen-hydrocarbon mol ratios normallyused during isomerization are within the range of about 0.25 to 10 toinsure long catalyst life. Liquid hourly space velocities, i.e., thevolume of liquid charge per hour per volume of catalyst, of about 0.1 to15 are satisfactory and pressures within the range of atmospheric to1500 psig in the isomerization zone are suitable.

Maintenance of catalyst activity during the isomerization process isaided by the inclusion of 0.001 to about 1 weight percent chloride inthe feed in the form of chlorinated hydrocarbon promoters such as carbontetrachloride, chloroform, ethyl chloride, isopropyl chloride, etc. Thisis not a substitute for the activation of the catalyst but it aids inmaintaining over long process periods the high level of catalystactivity produced by the invention catalysts.

The isomerization process can be carried out either batchwise orcontinuous, preferably the latter. In a continuous process it is to beunderstood that hydrogen in the effluent product can be separated andrecycled and that recycling of isomerization promoters, if employed, canbe practiced.

EXAMPLE I

The activity of the catalysts prepared in accordance with the inventionwas tested by isomerizing n-butane at about 150° F. The data are shownin Table 1.

                                      Table 1                                     __________________________________________________________________________    Effect of Catalyst Activation Conditions on Experimental n-Butane             Isomerization Testing                                                                                    invention               invention                  Run number:                                                                              1    2    3     4     5     6     7     8     9                    __________________________________________________________________________    Activating gas,.sup.(1)                                                                  15   15   15    15    14.7  14.7  15    15    15                   1/hr.                                                                         HCl, volume %                                                                            56   56   56    56    58    58    56    56    56                   H.sub.2, volume %                                                                        44   44   44    44    42    42    44    44    44                   Activating temp., ° F.                                                            1200 1200 1200  1200  1200  1200  1200  1200  1200                 Activating pressure,                                                          psig       atm. atm. atm.  atm.  atm.  atm.  10    10    atm.                 Activating time, hrs.                                                                    1.5  1.5  2.1   2.0   1.5   1.5   2.0   2.0   2.0                  Cooling gas flow,                                                                        15   6.5  15    95    14.7  14.7  15    55    47                   1/hr.                                                                         HCl, volume %                                                                            56   --   56    8.9   58    58    56    15    18                   H.sub.2, volume %                                                                        44   100  44    6.8   42    42    44    12    14                   N.sub.2, volume %                                                                        --   --   --    84.3  --    --    --    73    68                   Cooling Time,.sup.(2) hrs.                                                               0.2.sup.(3)                                                                        0.2  0.2   0.6   0.4.sup.(3)                                                                         3.sup.(3)                                                                           0.2   1.2   0.2                  Isobutene produced,                                                           weight %.sup.(4) total eff-                                                              65.8 57.2 71.4.sup.(5)                                                                        70.9.sup.(5)                                                                        61.8.sup.(5)                                                                        55.5.sup.(5)                                                                        73.3.sup.(5)                                                                        74.0.sup.(5)                                                                        71.0.sup.(5)         luent                                                                         Catalyst weight,                                                                         20   20   17.2  17.2  20    20    17.2  17.2  17.2                 grams                                                                         Catalyst support                                                                         eta  eta  gamma gamma eta   eta   gamma gamma gamma                           alumina                                                                            alumina                                                                            alumina                                                                             alumina                                                                             alumina                                                                             alumina                                                                             alumina                                                                             alumina                                                                             alumina              Platinum, weight %                                                                       0.5  0.5  0.4   0.4   0.3   0.3   0.4   0.4   0.1                  __________________________________________________________________________     .sup.(1) Catalyst heated in H.sub.2 at 1000-2000° F. before            activation.                                                                   .sup.(2) Cooling time to about 200° F.                                 .sup.(3) Cooling time to about 400° F.                                 .sup.(4) Isometrization conditions 150° F., atmospheric pressure,      0.2 LHSV of n-butane, no H.sub.2 used.                                        .sup.(5) Before testing, the catalyst was purged for 1 hour with hydrogen     at 400° F.                                                        

Inspection of the data presented in Table 1 shows that it is necessaryto have HCl in the ambient while cooling newly activated hot catalyst orthe isomerization activity of the catalyst is substantially diminishedas a comparison between Run 1 (65.8 mole percent isobutane formed, HClin cooling ambient) and Run 2 (57.2 mole percent isobutane formed, noHCl in cooling ambient) demonstrates. Neither runs 1 or 2 is within thescope of the invention since the cooling times in both are short andthus the invention is not needed. Run 6, compared with Run 5, shows thatrelatively long cooling times, i.e., 3 hours, for lowering thetemperature of the hot catalyst is detrimental even in the presence ofHCl when the HCl in the cooling ambient is the same as in the activatinggas. Run 6 is outside the scope of the invention for this reason; Run 5is outside the scope of the invention because the cooling time is short.The procedure is satisfactory only when short cooling periods, i.e., 0.4hours or less, are utilized as Runs 1 and 5 show. When long coolingtimes (0.5 hour or more ) are used such as can be expected in commercialproduction of chloride-activated platinum/alumina catalyst, it isnecessary to reduce the HCl concentration in the cooling ambient toabout 15 percent or less if an active isomerization catalyst is toresult. Inventions Runs 4 and 8 clearly demonstrate this (compare forinstance Run 8 with controls 5 and 6). Run 8 also shows that it may bedesirable to activate the catalyst under a slight pressure rather thanat atmospheric pressure since the catalyst activity appears somewhatimproved by so doing.

EXAMPLE II

Another series of activation tests was carried out using 10 or 25 psigin the activating chamber in which the compositions of the activatinggas and cooling gas were investigated as to their effects upon theisomerization activity of the catalysts. During the cooling period thepressure was reduced to atmospheric, the gas flows were altered, ifdesired, and nitrogen was added, if desired. The catalysts were testedusing isomerization conditions similar to those encountered incommerical processes. The results are presented in Table 2.

                                      Table 2                                     __________________________________________________________________________    Effect of Catalyst Activation Conditions on n-Butane Isomerization                                           Invention    Invention                         Run number:   10  11  12  13   14   15  16  17  18 19 20 21 22                __________________________________________________________________________    Activating gas.sup.(1)                                                        HCl, volume % 15  30  62  62,17                                                                              62,17                                                                              62  41  41  41 62 62 62 62                H.sub.2, volume %                                                                           85  70  38  38,83                                                                              38,83                                                                              38  59  59  59 38 38 38 38                Activating temp.,° F..sup.(2)                                                        1250                                                                              1250                                                                              1250                                                                              1250 1250 1250                                                                              1250                                                                              1250                                                                              1250                                                                             1250                                                                             1250                                                                             1250                                                                             1250              Activating pressure,                                                          psig          25  25  25  10   10   10  10  10  10 25 25 25 10                Activating time, hrs.                                                                       2   2   2   1 1  1 1  2   2   2   2  2  2  2  2                 Cooling gas flow, 1/hrs.                                                                    29  29  29  29   114  29  29  114 114                                                                              109                                                                              109                                                                              114                                                                              114               HCl, volume % 15  30  62  17   4    62  41  4   2  16 16 4  4                 H.sub.2, volume %                                                                           85  70  38  83   10   38  59  10  2  11 11 10 10                N.sub.2, volume %                                                                           --  --  --  --   86   --  --  86  96 73 73 86 86                Cooling time, hrs.                                                            to ≅200° F.                                                                0.2 0.2 0.2 0.2  3.1  0.2 0.2 3.7 3.3                                                                              2.9                                                                              3.7                                                                              3.6                                                                              4.7               Isobutane produced,                                                           wt. % in C.sub.4 effluent.sup.(3)                                                           48  58  60.5                                                                              59   55   60  56  59  57 57 55 60 60.5              __________________________________________________________________________     .sup.(1) Total activating gas flow of 29 1/hour, 34.6 g. catalyst treated     catalyst contains 0.4 wt. % platinum-impregnated on gamma alumina of          ˜ 218 m.sup.2 /g surface area.                                          .sup.(2) Catalyst heated about 2 hours in H.sub.2 at 1250 before starting     activation.                                                                   .sup.(3) Isomerization conditions: 325° F., 500 psig, 0.5 H.sub.2      /butane mole ratio, 4 n-butane LHSV.                                     

Inspection of the data presented in Table 2 reveals that theconcentration of HCl in the HCl-H₂ activating gas ambient is preferablygreater than 30 volume percent and is more preferably at least about 60volume percent to obtain active catalysts as Runs 11, 12, 15 and 16show. Good results are obtained when the pressure of the activatingambient is either 10 or 25 psig as Runs 12 and 15 show, providing theactivated catalysts are quickly cooled in the rich HCl-containingactivating ambient. Run 13 shows that it is possible to reduce the HClconcentration from 62 volume percent to 17 volume percent during thelast half of the activating process and still obtain an active catalystproviding that the catalyst is quickly cooled, i.e., about 0.2 hour, inthe less rich HCl-containing activating ambient. Invention Run 14 showswhen a longer cooling period, i.e., about 3 hours, is used coupled withlowering the HCl concentration in the cooling ambient to 4 volumepercent, the activity of the catalyst is diminished somewhat but it isstill relatively active as the isomerization results reveal. Inventionruns 19 and 20 show that even using suitably HCl activated catalysts,long cooling periods, i.e., about 3-4 hours, to lower the catalysttemperature to about 200° F. decrease catalyst activity somewhat evenwhen the concentration of HCl in the cooling ambient is about 16 volumepercent, the longer the cooling period the greater the decrease. (Notethat Run 13 in which 17 volume percent HCl is used in the coolingambient produces an active catalyst when a short cooling period isemployed.) Comparison of Run 16 with invention run 18 shows that slowcooling of properly activated catalyst in an ambient containing a lowpercent HCl (i.e., in accordance with the invention) can actually giveimproved isomerization activity of the catalyst compared with quicklycooled catalyst (Run 16) which would otherwise be expected to givebetter results. Invention runs 17, 21 and 22 show that active catalystscan be obtained using suitable amounts of HCl in the activating mediumeven when practicing prolonged cooling of the activated catalystsproviding the concentration of HCl in the cooling medium is low (about 4volume percent in these runs). Two volume percent HCl thus givessatisfactory results and 4 volume percent is somewhat better based onthe isomerization results.

Thus the invention discloses a method of cooling freshly made, suitablyHCl-activated isomerization catalysts so that activity of the catalystsis maintained even though long cooling periods are employed. Thepressure of the activating medium, commonly a HCl-H₂ mixture, can rangefrom about atmospheric pressure to somewhat above. Good results wereobtained at pressures ranging from 0 to 25 psig in actual tests. It isessential to have a comparatively low concentration of HCl presentambient during prolonged cooling periods.

EXAMPLE III

Gamma alumina extrudate (1.4 mm in diameter) impregnated with an aqueoussolution of chloroplatinic acid and hydrochloric acid to add 0.35 wt. %Pt and 1.0 wt. % HCl, was dried at about 240° F. and calcined at about800° F. A portion of this calcined material was heated for 2 hours atabout 1340° F. in a N₂ -H₂ mixture containing 5 mole % H₂ and then foran additional 2 hours at about 1340° F. in a H₂ -HCl mixture containing63 mole % HCl. The catalyst was then cooled to about 200° F. in 3.7hours in a gas mixture having the mole % composition HCl-5, H₂ -5, andN₂ -90.

The high hydrocracking activity of this catalyst was demonstrated withn-butane feed. Normal butane containing 100-200 ppm chloride (as CCl₄)was passed over a portion of the catalyst at 345° F. and 380° F., 500psig, and a H₂ /butane mole ratio of 0.55 with the liquid hourly spacevelocity adjusted to vary conversion. At 345° F., only about 1.4 wt. %of the butane was hydrocracked to lighter hydrocarbons when the butaneproduct contained 59% isobutane. However, at 380° F. about 6.2% of thebutane was hydrocracked to lighter hydrocarbons when the butane productcontained 59% isobutane. This increase in hydrocracking of therelatively stable butane molecule by a factor of over 4 when thetemperature was raised from 345° F. to the low temperature of 380° F.demonstrates the high hydrocracking activity of this catalyst whenreaction severity is increased. Hydrocracking is generally applied tohydrocarbons heavier than butane such as naphthas and distillates. Sincethese heavier hydrocarbons are normally much easier to hydrocrack thanbutane, this substantial hydrocracking of butane illustrates the highhydrocracking potential of this catalyst.

While this invention has been described in detail for the purpose ofillustration, it is not to be construed as limited thereby but isintended to cover all changes and modifications within the spirit andscope thereof.

I claim:
 1. A hydrocarbon conversion process which comprises contactinga hydrocarbon under hydrocracking conditions with an active aluminasupported platinum catalyst prepared by contacting said catalyst at atemperature within the range of 600°-1500° F. with a dry activating gascomprising 30 to 100 volume percent anhydrous hydrogen chloride for atleast 0.1 hour; and thereafter cooling the thus-activated catalyst for atime of at least 0.5 hour in the presence of a dry carrier gascontaining 1 to 20 volume percent anhydrous hydrogen chloride.
 2. Aprocess according to claim 1 wherein said feed is a C₅ or higher boilinghydrocarbon.
 3. A process according to claim 1 wherein said feed inn-octane and wherein said n-octane is converted to butane.
 4. A processaccording to claim 1 wherein said hydrocracking conditions are:pressure, 100-3000 psig; temperature: 300-700° F.; liquid hourly spacevelocity, 0.5-20 and H₂ /hydrocarbon mole ratio, 2-20.
 5. A methodaccording to claim 4 wherein said alumina is one of γ alumina or ηalumina and said hydrogen chloride is present in said carrier gas in anamount within the range of 2 to 6 volume percent.
 6. A method accordingto claim 4 wherein said alumina is γ alumina.
 7. A method according toclaim 1 wherein said HCl is present in an amount within the range of 40to 75 volume percent during said activation step and said contacting iscarried out for a time within the range of 0.5 to 6 hours and saidcooling is carried out over a time within the range of 0.5 to 10 hours.8. A method according to claim 4 wherein said activation temperature iswithin the range of 1050° to 1400° F.
 9. A method according to claim 8wherein said alumina is γ alumina, a concentration of said hydrogenchloride in said activation step is 41 to 62 volume percent, and aconcentration of hydrogen chloride during said cooling step is 2 to 6volume percent.
 10. A method according to claim 9 wherein hydrogen ispresent as a carrier gas in said activation step and said carrier gasfor said cooling is a mixture of hydrogen and nitrogen.